An HDX (half duplex) transponder device typically includes a charge capacitor that provides operational power for the transponder device in response to receipt of an interrogation signal. The charge capacitor provides the necessary voltage to allow the transponder to send a data telegram upon activation by the interrogation signal. However, the transponder device has no control mechanism determining whether or not the energy stored into the charge capacitor is high enough to transmit the full data telegram. As soon as the charge capacitor reaches the minimum operating voltage for the transponder device, a high peak discharge of energy stored within the charge capacitor occurs, resulting in a low energy/voltage level towards the end of the data telegram transmission phase. Without sufficient energy at the end of the data telegram transmission phase, an incomplete telegram may be sent or the data telegram transmission signal may be so weak that it reduces the transmission range for the transponder device. Therefore, it is desirable to have a transponder device that controls the voltage of the charge capacitor at the beginning of a data telegram transmission phase and regulates it to a constant value during the data telegram transmission phase.